1. Field of the Invention
The present invention relates to a novel polymeric compound that can be used as the base component of a resist composition, a resist composition containing the polymeric compound, and a method of forming a resist pattern using the resist composition.
Priority is claimed on Japanese Patent Application No. 2012-074972, filed Mar. 28, 2012, and Japanese Patent Application No. 2012-197774, filed Sep. 7, 2012, the contents of which are incorporated herein by reference.
2. Description of Related Art
In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure followed by development, thereby forming a resist pattern having a predetermined shape on the resist film. A resist material in which the exposed portions of the resist film become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have led to rapid progress in the field of pattern miniaturization.
Typically, these pattern miniaturization techniques involve shortening the wavelength (and increasing the energy) of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in the mass production of semiconductor elements. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a shorter wavelength (and a higher energy level) than these excimer lasers, such as extreme ultraviolet radiation (EUV), electron beam (EB), and X-ray.
Resist materials for use with these types of exposure light sources require lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources.
As a resist material that satisfies these conditions, conventionally a chemically amplified composition has been used, which includes an acid generator component that generates acid upon exposure, and a base component that exhibits changed solubility in a developing solution under the action of acid.
Resins (base resins) are typically used as the base components used within chemically amplified resist compositions.
For example, in an alkali developing process where an alkali developing solution is used as the developing solution, a chemically amplified resist composition for forming a positive-type resist pattern typically contains an acid generator component and a resin component that exhibits increased solubility in an alkali developing solution under the action of acid. If the resist film formed using this resist composition is selectively exposed during formation of a resist pattern, then acid is generated from the acid generator component within the exposed portions, and the action of this acid causes an increase in the solubility of the resin component in an alkali developing solution, making the exposed portions soluble in the alkali developing solution. As a result, by performing alkali developing, the unexposed portions remain as a pattern, resulting in the formation of a positive-type pattern.
As the resin component, a resin that exhibits increased polarity under the action of acid is typically used. When the polarity of the resin is increased, the solubility in an alkali developing solution increases, whereas the solubility in an organic solvent decreases. Accordingly, if a solvent developing process that uses a developing solution containing an organic solvent (an organic developing solution) is employed instead of an alkali developing process, then within the exposed portions of the resist film, the solubility in the organic developing solution decreases relatively, meaning that during the solvent developing process, the unexposed portions of the resist film are dissolved in the organic developing solution and removed, whereas the exposed portions remain as a pattern, resulting in the formation of a negative-type resist pattern. This type of solvent developing process that results in the formation of a negative-type resist pattern is sometimes referred to as a negative-type developing process (for example, see Patent Document 1).
Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are widely used as base resins for chemically amplified resist compositions that use ArF excimer laser lithography or the like, as they exhibit excellent transparency in the vicinity of 193 nm (for example, see Patent Document 2). Here, the term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position. The term “(meth)acrylate” is a generic term that includes either or both of the acrylate having a hydrogen atom bonded to the α-position and the methacrylate having a methyl group bonded to the α-position. The term “(meth)acrylic acid” is a generic term that includes either or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position.
Numerous materials have been proposed for the acid generator used in a chemically amplified resist composition, and known examples include onium salt-based acid generators, oxime sulfonate-based acid generators, diazomethane-based acid generators, nitrobenzylsulfonate-based acid generators, iminosulfonate-based acid generators, and disulfone-based acid generators. Among these acid generators, onium salt-based acid generators having an onium ion such as a triphenylsulfonium ion for the cation moiety are widely used.
Furthermore, in recent years, resins having a structural unit containing a sultone ring have been proposed for the aforementioned resin component. Conventionally, it has been suggested that these structural units can be added for the purpose of improving the adhesion between the resist composition and the substrate (for example, see Patent Document 3).